Software Update: Mozilla Thunderbird 78.7.0

The Mozilla Foundation has released version 78.7 of Thunderbird. Thunderbird is an open source client for email and newsgroups, with features such as support for several mail and news accounts, a spam filter, spell checker, and a customizable appearance. In version 78, a dark mode has been added and other parts of the interface, such as the icons and the screen for composing an email, have also been overhauled. Furthermore, the Lightning calendar add-on is now a standard part of the program, there is a new wizard for the first use and only MailExtensions add-ons are supported. The changelog for this release looks like this:

What’s New

  • Extension API: Compose API now supports editing messages and templates as new messages
  • Extension API: composeHtml is now exposed in MailIdentity
  • Extension API: windows.update and windows.create now support titlePreface
  • Extension API: new Accounts API functions: accounts.getDefault() and accounts.getDefaultIdentity(accountId)


  • Extension API: body and plainTextBody are now used as compose mode selectors in setComposeDetails and begin* functions in Compose API
  • Theme: removed the double border around the task description field on the Tasks tab


  • Account Manager: When deleting the last remaining account, the default account was not getting cleared and still pointed to the no-longer-existing account
  • OpenPGP: Verification of an inline signed message would fail if it contained leading whitespace
  • OpenPGP: Various other minor bug and stability fixes
  • Mail Window: Quickfilter bar buttons disappear when hovered on Windows 10 High Contrast Black theme
  • Theme: folder properties dialog contained black text on a black background in dark mode
  • Theme: recipient pills in compose window were not visible in high contrast dark theme on Windows 10
  • Extension API: browserAction buttons were not restored after restart if they were moved outside the default toolbar
  • Extension API: browser.compose.beginNew could not override identity plaintext setting
  • Extension API: browser.compose.beginForward was ignoring ComposeDetails
  • Extension API: browser.compose.setComposeDetails did not properly handle Windows-style line endings
  • Various security fixes

Known Issues

  • Thunderbird performs sluggishly on macOS Big Sur

Version number 78.7.0
Release status Final
Operating systems Windows 7, Linux, BSD, macOS, Windows 8, Windows 10
Website Mozilla Foundation
License type GPL